1. Field of the Invention
The present invention relates to a gas supply mechanism with a safety device. This type of gas supply mechanism is used for blowing out, cooling, or cleaning an electronic part by selecting a type of small size high pressure gas container for use therein.
2. Description of the Prior Art
A gas supply mechanism using a high pressure gas cartridge has a conventional rupture disk or a recovery type safety valve as a safety device for the occurrence of a high pressure greater than a value that the mechanism allows.
When the safety device acts, a thrust is generated by a discharge gaseous flow. IF this thrust moves the mechanism, it causes a great danger. In order to prevent this movement, as FIG. 8 shows, it is necessary to open gas discharge ports 83 of the safety device for a gas supply mechanism 81 outward and opposite to each other on the same line so as to counterbalance the thrust. Inevitably, the portion that forms the gas discharge port 83 had to be made protruded outward from the mechanism.
Further, in a conventional rupture disk 84 consisting of a plurality of components, an accuracy of those components, a strength of mounting the rupture disk 84, and so on considerably affect an operating gas pressure tolerance, so that those matters had to be strictly controlled.
Furthermore, in a gas supply mechanism that uses a pressure governor to supply the primary pressure (high pressure) gas for the secondary pressure (low pressure) gas, there is a safety device at the secondary pressure side as is shown in FIG. 9. This safety device is realized by making a horizontal hole 92 in a cylinder 91, wherefrom in case an excessive (high) gas pressure occurs gas is discharged outward when a V packing 94 in a piston 93 passes through an aperture 95 of this horizontal hole 92.
As FIG. 10 shows, there is another safety device of the same type as the above, wherein a cylinder 91 is extended upward to prepare an enlarged portion 96 with an inner diameter greater than that of the cylinder 91, so that a horizontal hole 92 can be opened to the enlarged portion 96 through the clearance between the inner wall and the piston 93.
As an even further safety device of the same type as the above is shown in FIG. 11, this safety device is prepared by providing the inner wall of a cylinder 91 with one streak of vertical groove 97.
In FIGS. 9 and 10, when a pressure P2 at the secondary side rises to thrust the piston 93 upward, the V packing 94 is exerted by a pressure from the secondary side and once struck for a while to the peripheral edge portion of the aperture thereof. When the piston 93 moves up further, the V packing 94 is damaged by the edge of the aperture 95, thereby causing gas leakage when the V packing 94 returns. This phenomena is liable to occur especially when the cylinder 91 is made of metal. For this reason, it is necessary to chamfer the aperture 95 of horizontal hole 92 of the cylinder 91, but it is very hard to treat a small diameter cylinder for the chamfering.
In addition, in FIG. 11, the V packing 94 is forced to fall in a vertical groove 97 by gas pressure to shut the groove, thus resulting in the failure of gas supply function.